In a general vehicle seat, a seat pad capable of elastically supporting an occupant is arranged on a back surface of a seat cover constituting a design surface of the seat. For example, the cushion pad as disclosed in JP-A-2016-036350, which corresponds to the seat pad of the present disclosure, is a member having a substantially rectangular shape in a top view when seen from above, which is used as a seat cushion serving as a seat portion. A seating portion is disposed on the cushion pad so as to allow the occupant to seat, and an upper surface (seating surface) serving as a front surface of this seating portion is substantially flat in the left-right direction, i.e. the seat width direction, and in the front-rear direction. When the occupant sits on the seating portion, parts strongly pressed by buttocks of the occupant may occur separately on the left and the right of the seating portion (see FIG. 4 of JP-A-2016-036350).
Then, the technical field of vehicle seat requires to improve performances of a vehicle seat by improving seating performance, etc. of a seat pad. However, in a conventional cushion pad (seat pad), left and right parts of a seating portion are greatly concave-deformed when an occupant is sitting thereon, which is an unsuitable configuration from a viewpoint of seating performance improvement of the seat. Namely, concave-deformation of the left and right parts of the seating portion means that a part therebetween (a central part of the seating portion) relatively protrudes toward the occupant side. If the central part of the seating portion excessively protrudes toward the occupant side, such protruding part comes into contact with the occupant and becomes a reason for foreign body sensation, which may deteriorate seating performance of the seat.